According to Maitrāyaṇīya Samhitā (I.6.12), Aditi, desirous of progeny, prepared sacrificial rice, offered it to the deities, and ate the remnant. The result was that two sons were born of her, Mitra and Varuṇa. Again, she repeated the same and ate the remnant. Two more sons were born of her, Dhātā and Aryaman. She repeated the performance and again the result was the same, giving rise to Amśa and Bhaga this time. In consequence, she concluded that she bore each time two sons because she had eaten the remnant of her offering. So she was tempted to eat first and then offer the remnant. The result was that the two eggs within her were blighted. While one recovered, the other appeared as dead and when born came to be known as Mārtāṇḍa.
The Great Sun Mārtāṇḍa, the son of Aditi, born of the unconsecrated remainder, is the father of Life (Manu) and Death (Yama). Each of the other seven sons too is born of the remainder. From the Remainder, Aditi, the Boundless, brings forth the Sun in its various forms, the measure of time, the condition of mortal life.
The non-limited, beyond limits, beyond the conditions which bring about the limits is Brahman. Being beyond all conditions, Brahman is all and everywhere and necessarily also in those conditions. So they too are within Brahman. Thus it is said in the Māitrāyaṇī Upaniṣad: there are two forms of Brahman, one is deathless and the other is mortal. The mortal form is the Sun. This Sun, whose children are men (and women), is called Mārtāṇḍa.
Time in its cyclical appearance is manifested by the sun, moon, and planets. It is the contingent aspect of duration. Duration is beyond division, it has no parts. Yet it is different from the unconditioned, unqualified Nirguṇa Brahma-vastu of which it is the first qualified aspect. The Nirguṇa Brahman is beyond duration and time. Duration is the principle of time and death. The Sun (Mārtāṇḍa) is the father of Death (Yama) and of Prototypal Man, Manu, the law-giver of each cycle (manvantara i.e. 4,320,000 years which is 10X432,000 – the number of syllables of the Rgveda). Duration as the principle of cyclical time is represented by Mārtāṇḍa Bhairava or Mahākāla.